Measurement of insolation using CdS photoresistor

Abstract

Utilizing a cadmium sulphide (CdS) photoresistor, the intensity of solar electromagnetic radiation (insolation) was investigated. Readings were taken daily and hourly at the Nsukka Campus of the University of Nigeria which lies on latitude 6.8° north and longitude 7.35° east. Our investigation spanned a period of 8 months (February–September). This was an extension of work done by E. Klugmann & O. E. Onyeogu who carried out a similar investigation, but for a shorter period, 4 months (October-January) and also their investigations took account of only the dry season and harmattan. Our investigation took account of a very vital climatic period in Nigeria, namely the rainy season (March–September). It was observed that with a cadmium sulphide photoresistor which has an average efficiency of 7% 2, the maximum average hourly insolation is roughly 63 W m −2 which is equivalent to 900 Wm −2 if cadmium sulphide were to be 100% efficient. Furthermore, it was consistently observed that the amount of solar intensity falling on our detector is always greater after the rains. Finally, our results are then compared with the modified empirical equations of Rapp & Hoffman and there is some times nice agreement between experimental and theoretical results of hourly insolation in Wm −2, and sometimes there is sharp contrast between the two.